(a) Field of the Invention
The present invention relates to a monofilament suture and a method to prepare the same. In particular, the present invention relates to a monofilament suture, wherein polymers having identical inherent properties are spun to have a cross-sectional structure of conjugated filaments, and said cross-section has interfaces between the spun polymers, discontinuous in the radial direction of the monofilament and continuously distributed in the axial direction of the monofilament, to improve knot security of the monofilament suture. Therefore, the monofilament suture of the present invention can be applied for various medical uses.
(b) Description of the Related Art
Monofilament sutures generally exhibit less tissue drag and cause less tear because they have smoother surfaces than braided multifilament sutures. Monofilament sutures, in general, do not provide the capillarity found in multifilament sutures, which minimizes the spread of wound infection with bacteria and the like.
However, since monofilament sutures comprise a single filament, there are the following disadvantages: they are less flexible than multifilament sutures; it is more difficult to tie a knot; and the tied knot is more likely to loosen due to inferior knot security.
In addition, even if a marketed monofilament suture is relatively flexible, its knot is easily untied. Therefore, in order to make the knot secure, additional throws while tying are required.
Such additional throws increase the amount of suture remaining inside the body, and, consequently, increase the irritation caused by the foreign material in the wound. This increase in foreign body, even in the case of an absorbable suture with good biocompatibility, may provoke irritation in adjacent tissues, and thus, increase the probability of inflammation. Furthermore, a patient may feel sensations or stimulation from the knots. The larger the volume of tied knots there is, the more likely it is that undesirable symptoms will present. (Van Rijssel EJC, et al., Mechanical performance of square knots and sliding knots in surgery: A comparative study, Am J Obstet Gynecol 1990; 162:93-7, Van Rijssel EJC, et al., Tissue reaction and surgical knots: the effect of suture size, knot configuration, and knot volume, Obstet Gynecol 1989; 74:64-8, Trimbos, J. B., Security of various knots of commonly used in surgical practice, Obstet Gynecol., 64:274-80,1984).
The monofilament is conventionally prepared through single extrusion of single polymer, and in some cases, is prepared through conjugated spinning of different polymers.
As a method to prepare a monofilament suture by conjugated spinning, U.S. Pat. Nos. 5,626,611, 6,093,200, 6,315,788, 5,641,501, 6,090,910, 5,997,568, and 6,162,537 disclose a method of performing the conjugated spinning of different polymers, to control the degradation rate of the obtained absorbable suture. These methods of preparing sutures by conjugated spinning of different polymers have an advantage of overcoming the defects present in each polymer by using at least two polymers in combination, when compared with the method of preparing the suture by single spinning. However, when using different polymers, the preparation of a suture is difficult, since the melting properties, such as the melting point and the like, are different.
U.S. Pat. Nos. 5,540,992 and 6,093,200 disclose a technique of conjugated spinning using similar but different polymers.
U.S. Pat. No. 5,540,992 discloses a method of preparing a fiber for a non-woven fabric having an improved flexibility by conjugated spinning of high-density polyethylene and low-density polyethylene in sheath/core form using the difference between the melting points. However, although high-density polyethylene and low-density polyethylene have same chemical formula, since the molecular structures thereof are different, that is, one has a linear chain structure and the other has a branched chain structure, the melting properties thereof, such as the melting point, are different, and thus, the processing conditions thereof are also different from each other.
U.S. Pat. No. 6,093,200 discloses a method of preparing a suture by conjugated spinning of two kinds of polypropylene sharing the same chemical formula but having different melting properties due to different stereo-regularity.
As can be seen from the aforementioned related art, up to the present, many studies have been performed on techniques to improve the flexibility and strength of the suture or to control absorption rate.
However, research into improving knot security, as one of the important requirements of a suture, has not been enough. Therefore, the present invention provides a suture with excellent knot security and flexibility, which helps overcome the disadvantages of currently marketed monofilament sutures.